Edible water-in-oil emulsions (W/O emulsions) like e.g. margarine and low fat spreads are well known food products that comprise a continuous fat-phase and a dispersed water-phase.
Margarine is generally defined as a composition containing at least 80 wt. % of fat and about 20 wt. % of a water-phase. In contrast, emulsions containing less than 80 wt. % of fat are generally called spreads. Nowadays the terms margarine and spread are often used interchangeably although in some countries the commercial use of the term margarine is subject to certain regulatory requirements. The main difference between margarine and spread is the amount of fat. For the purpose of the present invention the terms margarine and spread are used interchangeably.
The fat-phase of margarine and similar edible W/O emulsions comprises a mixture of liquid oil (i.e. fat that is liquid at ambient temperature) and fat which is solid at ambient temperature. The liquid oil fraction typically comprises liquid unmodified vegetable oil such as soybean oil, sunflower oil, linseed oil, low erucic rapeseed oil (Canola), corn oil (maize oil) and blends of vegetable oils. The solid fat, also called structuring fat or hardstock fat, serves to structure the fat-phase by forming a fat crystal network throughout the continuous oil-phase. It also helps to stabilize the emulsion. The droplets of the water-phase are fixed within the spaces of the lattice of solid fat crystals. This prevents coalescence of the droplets and separation of the heavier water-phase from the fat-phase.
For an edible water-in-oil emulsion, ideally the structuring fat has such properties that it melts or dissolves at in-mouth conditions, otherwise the product may have a heavy and/or waxy mouthfeel. An important indicator is the temperature at which a water-in-oil emulsion breaks up. Preferably the water-in-oil emulsion breaks up at in-mouth conditions to provide a good oral response. Furthermore, the overall organoleptic impression should be smooth and preferable no perceivable grains should be present upon ingestion as this may result in what is generally known as a ‘sandy’, ‘grainy’ and/or ‘lumpy’ mouthfeel.
Triacylglycerols (TAGs), also known as triglycerides, are the major constituents of natural fats and oils and are esters of glycerol and fatty acids. The chemical structure of the fatty acid and the distribution of the fatty acids over the glycerol backbone determine (at least partly) the physical properties of a fat. The physical properties of fats, like for example the solid fat content (SFC) expressed as N-value, can be modified by altering the chemical structure of the fat. Well known techniques that are widely used include hydrogenation and interesterification.
Water-in-oil emulsions are typically made by either the votator or churn process; or by a process which involves the use of fat powder comprising hardstock fat.
The general process for the manufacture of emulsions via the votator or churn process encompasses the following steps:    1. Mixing of the liquid oil, the hardstock fat and if present the water-phase at a temperature at which the hardstock fat is definitely liquid;    2. cooling of the mixture under high shear to induce crystallization of the hardstock fat to create an emulsion;    3. formation of a fat crystal network to stabilize the resulting emulsion and give the product some degree of firmness;    4. modification of the crystal network to produce the desired firmness, confer plasticity and reduce the water droplet size.
These steps are usually conducted in a process that involves apparatus that allow heating, cooling and mechanical working of the ingredients, such as the churn process or the votator process. The churn process and the votator process are described in the Ullmans Encyclopedia, Fifth Edition, Volume A 16, pages 156-158.
The general process for the manufacture of emulsions by use of fat powder comprising hardstock fat (i.e. pre-crystallized fat) encompasses the following steps:                a. mixing of fat powder and liquid oil to provide a slurry;        b. providing a water-phase;        c. mixing the slurry and the water-phase to form a fat-continuous emulsion,wherein the fat-powder is typically not subjected to a temperature at which the fat powder will substantially melt.        
A commonly used type of fat powder is micronized fat powder, which is for example obtainable by a Super Critical Melt Micronisation process, as described in J. of Supercritical Fluids 43 (2007) 181-190 and EP1651338.
One of the benefits of the use of fat powder for emulsions, in comparison with the votator or churn process is a reduction in energy requirement, a broader range of fat suitable as hardstock fat and that it allows a reduction in SAFA.
Important quality-aspects of edible water-in-oil emulsions are for example hardness, spreadability and stability (e.g. storage stability and the ability to withstand temperature cycling). Temperature cycling means that the product is subjected to low and high temperatures (e.g. when the consumer takes the product out of the refrigerator and leaves it for some time at the table prior to use). An inadequate stability may for example lead to destabilization of the emulsion, oil-exudation and/or crystal growth. Another important quality aspect is the temperature at which a water-in-oil emulsion breaks up. Preferably the water-in-oil emulsion breaks up at in-mouth conditions to provide a good oral response. Another important quality aspect oral response is the mouth-feel of a water-in-oil emulsion in terms of waxiness. Preferably the water-in-oil emulsion does not have a waxy mouth-feel.
Nowadays consumers and retailers place high demands on the technical specifications of W/O emulsions regarding both organoleptic experience and stability (e.g. during storage, transport and cycle stability). Therefore, there is a continual interest to improve the stability and/or organoleptic experience of W/O emulsions.
One typical way to change both the stability and the break-up temperature of W/O emulsions is to change the composition of the hardstock fat. However, we observed that modifying the hardstock fat composition to change the temperature at which a water-in-oil emulsion breaks up, can adversely affect the stability of W/O emulsions and visa-versa.
Therefore there is a need to for a process which allows changing one characteristic of a W/O emulsion, such as oral response, with little or no change in a second characteristic, such as stability.
Preferably such a process involves little or no change in ingredient composition.
A single process is often used to prepare multiple types of W/O emulsion product. Examples of different products are wrappers, liquid margarine and (low-fat) spreads. It is desirable to use similar or even the same ingredients (such as the hardstock fat), possibly in different amounts, for the preparation of different types of W/O emulsion products. Use of a small number of ingredients can reduce complexity, the equipment requirement, space usage and improve the flexibility of the process.
It will be appreciated that said benefits are particularly relevant for factory scale processes. Typically, for factory scale processes, the ingredients serve the general requirements of the different products. As such, changing an ingredient to improve one product may negatively influence other products.
Therefore there is a need to for a process which allows changing one characteristic of a W/O emulsion, such as oral response, with little or no change in a second characteristic, such as stability, preferably while requiring little or no change in ingredient composition, such as hardstock fat composition.
Furthermore, there is a need W/O emulsions having an improved oral response while having good stability.